People's behavioral and emotional reactions to life circumstances depend critically upon their perceptions of others' reactions to those same circumstances. The present project explores the origin and health-related consequences of systematic distortions in people's perceptions of the feelings, attitudes, and behaviors of others. The long-term objective of the project is to document when and why discrepancies arise between objective and perceived group consensus and how these discrepancies influence individual and group functioning. To this end, the main focus of the proposed research is the misperception of group norms, particularly that form of norm misperception that arises when people infer that the private thoughts, feelings, and behaviors of their peers are different than their own even though their public behavior is similar. The present research has three specific objectives. First, it seeks to understand why people tend to believe that their private beliefs and feelings are more evident to others than they are and how this illusion of transparency contributes to norm misperception. Second, it seeks to understand why people often attribute their behavior to one cause and the identical behavior of their peers to another cause and how this phenomenon contributes to norm misperception. Finally, it examines factors that produce discrepancies between people's public behavior and their private beliefs as well as conditions that reduce discrepancies of this type and hence the potential for norm misperception. The proposal's objectives will be pursued through an interrelated program of experimental and correlational studies. In different ways, each of the proposed 12 experiments examines either the psychological process that underlie norm misperception or the implications that norm misperception has for psychological adjustment and the perpetuation of unhealthy social practices.